Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects.
In lighting systems such as those that include LED-based light sources, it is desirable to have control over one or more light sources of the lighting system. Control of one or more light sources enables specification of lighting parameters for an environment. For example, a user may directly specify one or more lighting parameters of one or more light sources. Also, for example, the user may specify the effect that is desired at one or more locations in the environment and lighting parameters of one or more light sources may be derived based on the desired effects.
Many light shows include a sequence of slowly changing effects (e.g. color wash, chasing rainbow). These kinds of effects are designed to change the light output from one hue to another (or one intensity value to another) over a period of several frames.
Digital lighting controllers typically send data to light fixtures at some frame rate to modify a light effect setting. Light fixtures generally refresh their output at the same rate sent by the digital light controller. This means that lighting controllers must send data to light fixtures at very high rates in order to ensure that transitions from one frame to the next are not visually perceptible to the viewer. This consumes a great deal of data bus bandwidth. Bandwidth usage is related to the number of light fixtures on the bus and the data frame rate. Because the bus bandwidth is constant, as the number of light fixtures on the bus increases, the frame rate, and thus the refresh rate of the light fixtures, decreases. And so it is often not possible to achieve very high refresh rates in large lighting installations, resulting in choppy light transitions.
In order to avoid unwanted visual artifacts in a lighting show, it is often desirable to have high refresh rates in light fixtures. As the number of lights on the data bus increases, the ability to maintain high refresh rates diminishes. Thus, it is desirable to maintain high refresh rates even with large light installations. Also, some controllers are not capable of sending high frame rate data. Thus, it is also desirable to reduce the visual artifacts produced by these low frame rate controllers.